test: migrate examples to XXXX-category-name layout + split expected streams

Rename all example tests/companions to the XXXX-category-test-name scheme
(per-category 100-blocks: basic 0010, types 0100, ... errors 1000,
diagnostics 1100, ffi 1200, ffi-objc 1300, ffi-jni 1400, vectors 1500,
platform 1600). Companions and dir/C fixtures move in lockstep with their
parent test; #import/#source/#include paths rewritten to match.

Expected output now lives in examples/expected/ (a sibling dir of the
tests) split into three streams per the new convention:
  <name>.exit / <name>.stdout / <name>.stderr  (+ optional <name>.ir)

run_examples.sh rewritten: scans examples/ and issues/ for an
expected/<name>.exit marker, captures stdout and stderr separately (no
more 2>&1), compares each stream + exit + optional IR snapshot.

Behavior validated unchanged: every renamed test reproduces its prior
merged output + exit (diffs limited to file paths/basenames embedded in
diagnostics + traces, which correctly reflect the new names). Suite:
292 passed, 0 failed. 50-smoke.sx split + issue relocation + docs follow
in subsequent commits.

examples/1205-ffi-foreign-global.sx

@@ -0,0 +1,32 @@
+// Extern data globals via `<name> : <type> #foreign;`. Lets sx code
+// reference libSystem / framework symbols (NSConcreteStackBlock,
+// __stdinp, etc.) for FFI bridges. Mirrors the long-standing
+// `<fn> :: (...) -> ... #foreign;` form on the function side.
+//
+// Cross-file dimension (PLAN-FFI step 0.10): the helper companion
+// `94-foreign-global-helper.sx` ALSO declares `__stdinp : *void #foreign;`.
+// Both files referencing the same extern symbol must link cleanly —
+// LLVM dedupes the named global, the C linker resolves both refs to
+// the one libSystem symbol.
+//
+// We *don't* check that the helper computes the same address — see
+// issue-0037 (helper-function-scoped `@foreign_global` lowers to
+// undef today). When that fixes, fold the helper's address back into
+// the equality check here.
+
+#import "modules/std.sx";
+#import "1205-ffi-foreign-global-helper.sx";
+
+__stdinp : *void #foreign;
+
+main :: () -> s32 {
+  addr_bits : u64 = xx @__stdinp;
+  print("stdin extern global non-null: {}\n", addr_bits != 0);
+  // Force the helper symbol to participate in linking (otherwise the
+  // imported file's #foreign decl might get dropped by the
+  // dead-code stripper). The actual return value is busted today
+  // — see issue-0037.
+  _ := stdinp_addr_present();
+  print("helper file linked: true\n");
+  0;
+}